This should vary by OS, by how you open the file, by when you flush the file, by how much you're writing out and by where you are writing in the file.

Why don't you ask how to do what you want to do instead of asking such an open ended question?

Update: Added more criteria.

In reply to Re: Performing action on one file at same time by two perl scripts by ikegami
in thread Performing action on one file at same time by two perl scripts by Anonymous Monk

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